This invention relates to a hydraulic fluid coupling, and, more particularly, to a fluid coupling which includes a shroud for protecting the valve closure of the coupling.
The invention is an improvement to the male coupling described in U.S. Pat. No. 4,221,235. The couplings described in that patent are typically used on agricultural tractors for connecting the tractor hydraulic system with the attachable implements. With the increasing sizes of tractors, implements and hydraulic systems, the fluid flow rates are increasing accordingly. Under high flow conditions in the female-to-male direction, the valving of the couplings described in the patent can become unstable. Referring to FIGS. 1, 3, and 6 of the patent, when fluid is flowing in the right-to-left direction, fluid can flow around the ball 19, through the dimples 73, and into the cavity of the shroud 20 behind the ball 19. Under normal conditions, this poses no problem. However, on high flow hydraulic systems creating high flow velocities, the flow into the cavity behind the ball can be so great that pressure builds and forces the ball to the right against the poppet assembly 15 of the female coupling (FIG. 1). Since the poppet assembly is spring-biased, the flow forces on the ball can overcome the spring forces. This creates an unstable condition causing the parts to oscillate, vibrate, and prematurely wear.
The improvement comprises an integral shuttle valve or check valve which relieves the trapped fluid behind the ball to the downstream side of the shroud. This allows the ball to remain seated against the stop portion 67 of the shroud at all times. The shuttle valve closes the shroud cavity when fluid is flowing in the left-to-right direction from the male to the female coupling. It is important that fluid pressure not enter the cavity from this direction and force the ball to the right against the poppet assembly springs and cause the ball to close against the seat.